The most commonly used technologies for gesture-based interfaces include data gloves, computer vision techniques and magnetic or infrared sensors. Data gloves are expensive and also restrains users to a device; also, data gloves are not suitable for use in public spaces. Computer vision systems are sensitive to lighting conditions and have a comparably low update rate, though they can be quite accurate. But vision systems often force the user to adapt a new means of interaction (e.g. head or eye movement). Infrared and magnetic sensors also require the user to wear a device. EFS-based navigation techniques require users to undergo tedious calibration procedures.
Moreover, gesture-based touchless input devices for user interfaces of computers are known using cameras for determining the position and gesture of, e.g., a user's hand. Examples of these technologies are described in patent documents DE-A-42 01 943, DE-A-199 18 072, DE-A-100 07 891, DE-A-100 56 291, US-B-6 252 598, JP-A-09258945 and JP-A-10031551.
Moreover, from DE-A-43 12 672, a touchless cursor-control-like input device for computers is known which comprises proximity switches for controlling cursor movement and other functions. Each proximity switch functions based on a capacitance measurement. These switches cannot detect the position of, for example, a user's finger within their sensitive area but can merely detect that within the sensitive area a user's finger is located.
Moreover, EP-A-0 698 858 describes a touchscreen based on capacitive sensors which can reduce noise. The sensor detects the current change of the antenna to locate the finger position. This technology requires touching the surface of the screen.
Finally, U.S. Pat. No. 6,457,585 describes a data input device wherein the user needs to wear a data glove. This known system works on the propagated radio signal length for transmitting the hand gesture status from the data glove.